1. Field of the Invention
The present invention relates to time delay and integration image sensor (TDI image sensor) using complimentary MOS technology (CMOS technology). In particular, the invention relates to achieving the integration function without charge transfer devices.
2. Description of Related Art
In many imaging applications the image scene moves relative to the camera at a constant velocity. For example, objects on a conveyer belt may be imaged by a stationary camera adjacent to the conveyer, or features on the ground may be imaged by a camera mounted on a moving vehicle. Such applications can be addressed by a line scan camera in which the imaging region consists of a single row of pixels. However, where the relative velocity is large, the maximum integration time available for each pixel is very small. If the velocity is sufficiently large relative to the illumination level then the image signal may too small to be useful.
Time delay and integration (TDI) image sensors are used in line scan applications where the light level is low or where the speed of the moving image is high. TDI has typically been addressed with CCD sensors in which the TDI functionality can be achieved by transferring a charge packet along the CCD synchronously with the image. Charge transfer cannot be achieved in the same way with CMOS processes, and hence a CMOS approach to TDI has been disfavored.